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Letters Patent No. 77,301. flatediAprt'l 28, 1,868.

IMPRGl-EMNT IN STEAM 'SLIDE-VALVES.

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TO ALL WHOM ITKMAY GONOERN: A

B`e it known that I, JACOB' MARTIN, of Cairo, in the countyot' Alexander, and State of Illinois, have invented a new anduseful Improvement in Balanced Slide-Valves; and I do hereby declare that the following is a full, clear, and exact description thereof, whichv will enable others skilled in the art vto make and use the same, reference being had to the accompanying` drawings, forming part of this specification, iny which- Figure 1 is a vertical section through the longitudinal axis of ,a valve and steam-chest made according to my'invention, the plane of section being indicated by the letters y y, iig. 2;

Figure 2 isa cross-section on the line :c of iig. Similar lettersof reference indicate like parts. f 'The object of this improvement isto relieve slide-valves from unnecessary pressure. The valve is quadrangular n shape, its fourvertical lsides being solid, and its top and bottom being removed, so as to leave its interior open and 4uncovered,both` towards the valve-seat, and also at the back of the ,valve The baok of the valve is covered by a flat plate, suspended from a piston-rod, whose ,piston is fitted to a verticnlpcylnder on the back of the steam-chest. Theplatets steam-tightto the upper face of the valve. The exhauststesm is passed from the exhaust-port through 'a pipe leading ihtothe vertical cylinder above its piston, the pipe being continued irom the opposite side of the cylinder to a condenser, or other place where the exhaust-steam is dis posed of. The top of Athe suspended plate and the bottom of the piston, which is connected to it bya rod, are. exposed to the steam admitted to the chest, land the area of the `piston is less than the area of the Vopen back of the valve under the plate, which .is there exposed to the exhaust-steam. VSo much pressure is removed from the valve ns is due to the diilerenceiu the two areas, which allows the valve to move freely, andwith little friction, between the plate and the valve-seat.- A very small excess of weight is 'left on the plate, to make the valve work steam-tight onits two faces. When the exhaustlsteam passes through the valve, it has a tendency to raise the plate, but, being conducted through the vertical cylinder above the piston, whichvis connected to'said plate, such exhaust-steam is made thereby to counteract the pressure on the under side of the plate, and to keep the piston and plate in a balanced state.

The letter A designates `the place of the cylinder of an engine, and B is its steam-chest, having a slide valve, C, and valve-stem D. The seat of the valve has induction-ports, H H, communicating with valve-passages' E E, which lead into opposite ends of cylinder AL The eduction or exhaust-port F communicates with a port or opening, G, made in the valve-seat midway between vthe ports E H.

The valve C is quadrangular in form, having its sides and ends vertical. The valve-stem passesthrough its shorter diameter, being enclosed within a tube which extends between the sides of the valve in that direction; The stem is free to revolve within the tube, and it is connected to the valve by following-nuts, in the usual way; The upper face' of the valve is parallel with its lower face, and its back is left open. The open back of the valve is covered by a plate, I, which ts steam-tight to its upper face. -This plate is suspended by a rod, N, which carries also a piston, K, iittcd in a cylinder, J, which is placed on the top ofthe steam-chest, and opens therein, The rod N is extended upwards through the cap of cylinder J, and through a stuEing-box, and serves as aguide to the piston and the suspended plate. A spiral spring, L, is-placed about the rod N, between the piston and the cap ofthe cylinder, whose oiiice is to restore the plate I to its proper place in case it is raised oil` the upper face ofthe valve by the action of the exhaust-steam. y

The exhaust-steam is conducted to the upper part of cylinder J, above the piston K, by a pipe, M, leading from the eduction-port F of the steam-chest, said pipe being continued from the opposite side of the cylinder, tol conduct the steam away to its place of 'nal discharge.

In the working of the valve, the exhaust-steam momentarily impairs the vacuum on the eduction or exhaust side of the valve, and has a tendency, by its pressure, to raise the plate from its seat on the upper face of the valve thereon; but such pressure is eounteracted by conducting the exhaust-steam from the eduction-port F, through pipe M, into and,z through the upper part of cylinder J,above the piston K, whereby the piston and plate are kept in a balanced state.

In case of back pressure, the plate will be raised fromoi' the valve; and I-lmve made provision for such an exigencyr'by placing a. spring, L, between the piston K and the cap`of 'the .cylinder in which the piston is tted, which spring, by its reaction, insures the return of' the plate, and so keeps the valve properly adjusted to its seat when the engine is at rest.

I claim as new, and desire to secure by Letters' Patent- 1. The combination of the stem-chest B, exhausbpipe M; and cylinder J, substantially as herein set fortln 2. I claim the combination of the suspended plate I, pistonV K, pston-rod N, and spring L, substantially as' shown and described. f

v JACOB MARTIN.

Witnesses:

Geo. CARY Eccnnsi'om R. P. Rommm. 

